Some definitions of interest.
eq_int	Def  i=j == if i=j true ; false fi
	Thm*  i,j:. (i=j)
int_iseg	Def  {i...j} == {k:| ik & kj }
	Thm*  i,j:. {i...j}  Type
nequal	Def  a  b  T == a = b  T
	Thm*  A:Type, x,y:A. (x  y)  Prop

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